The present invention relates to a controllable drive system for an internal combustion engine and more particularly to a variable speed drive system for driving an auxiliary member such as a cooling fan.
Referring to FIG. 1 it is well known to employ a cooling fan for cooling engine coolant across a radiator. A pulley drive is directly connected to a rotatable spindle of a water pump which is driven by an engine crank shaft. The pulley drive is in turn connected to the fan pulley to rotate the fan and force airflow across a radiator. It is also known to include a clutch to selectively disengage the fan. One such fan drive is disclosed in U.S. Pat. No. 4,222,353 which is incorporated herein by reference.
In truck engine cooling applications, viscous drives are often employed to attempt variable speed drive of the cooling fan. However, these viscous type systems do not provide sufficient mechanical power, do not have full lock-up and full-off capabilities, require the fan to be aligned and within close proximity to the engine, and dissipate a tremendous amount of heat which wastes energy.
It is also known to employ a manually adjustable idler mechanism to adjust the tension on the belt across a pulley drive assembly. One such mechanism is disclosed in U.S. Pat. No. 4,500,303 and is incorporated herein by reference.
In the general transmission art, infinitely variably speed transmissions employing adjustable pulley drives are known within the prior art. A V-belt type stepless transmission, having an input pulley and an output pulley mounted on parallel input and output shafts, respectively, each of the input and output pulleys having a stationary flange and a movable flange axially displaceable relative to the stationary flange and rotatable integrally therewith; an endless V-belt lapped around the input and output pulleys to transmit power therebetween; and a spring and cam mechanism provided at least on one of the input and output shafts to vary compressive belt gripping force of the stationary and movable flanges in proportion to the torque transmitted by the belt. One such infinitely variable speed transmission is disclosed in U.S. Pat. No. 4,541,821 and is incorporated herein by reference. Lastly, speed sensitive variable ratio drive pulleys are known such as disclosed in U.S. Pat. No. 5,326,330 which is incorporated herein by reference.
It is an object of the invention to improve upon and overcome the drawbacks of the related art.
The present invention is directed to a variable speed drive assembly for an auxiliary member in an internal combustion engine. An auxiliary member, such as a fan, connected to a pulley is driven by a drive pulley connected to a crankshaft of the internal combustion engine via a V-belt. At least one of the pulleys is an adjustable drive ratio pulley. An actuator is operatively connected to the drive assembly to controllably change the drive ratio of the pulley. By controlling the drive ratio of the pulley, the speed of the fan can be selectively controlled. The adjustable drive ratio pulley may have an inner idler freely rotatable mounted therein. The actuator may also cause the V-belt to engage the inner idler to substantially disconnect a connection between the fan and the crankshaft thus allowing the fan to windmill. Thus the present invention contemplates selective variable speed control of a cooling fan for different engine operating conditions superior to devices found in the prior art.